Your Trash, My Electricity

For decades, Russ Lester watched in frustration as truckload after truckload of the walnut shells from his California farming operation (Dixon Ridge Farms) were shipped several hundred miles north to a facility that burned them, converted the resulting energy into electricity, and buried the toxic ash in a landfill. He was equally frustrated at the slowness of the industry in general to move toward energy independence.

"I decided it was all ridiculous," he says. "We set a goal in 2007 to become 100% energy independent in five years."

Lester contacted the Community Power Corporation (CPC) to discuss the potential of gasifying his shells to produce on-site electricity and thermal energy. Through a cost-shared California Energy Commission grant, they installed an initial 50 kW BioMax system that has been operational since Jan. 2008, and added a second 100kW BioMax unit in 2012.

Lester says the system burns about 10 to 15% of the farm’s walnut shells to achieve 2,000ºF. The remainder of the shells are baked in this intense heat, causing chemical bonds to break down into three combustible gasses – including carbon monoxide, hydrogen and methane. These gasses are then collected and run through a combustion engine. Dixon Ridge Farms also dries its walnuts using the heat generated.

The ash resulting from the bio-gasification process is not toxic – in fact, it is mixed back into the soil. Lester says the carbon-laden ash also has effectively sequestered that carbon for the next thousand years.

"This is actually a net carbon negative," he says.

The BioMax technology can incorporate a broad range of agricultural byproducts in the conversion process – everything from wood ships, spoiled produce, food scraps and even cardboard and paper waste. The company is currently looking into the conversion efficiency of corn and other row-crop residue.

Lester says he hopes other farms and communities will take a closer look at the bio-gasification process. Some of the hurdles of energy independence are more about perception than reality, he says.

"Everyone says it’s more expensive to do, but it’s not," he says. "Everyone says we don’t have the tools available, but we do."